The Identification Protocol (a.k.a., "ident", a.k.a.,
"the Ident Protocol") provides a means to determine the identity
of a user of a particular TCP connection. Given a TCP port number pair, it
returns a character string which identifies the owner of that connection on
the server's system.

Server authors should subclass this class and override the lookup
method. The default implementation returns an UNKNOWN-ERROR response for
every query.